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https://issues.apache.org/jira/browse/HBASE-17653?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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stack updated HBASE-17653:
--------------------------
Description:
Follow-on from HBASE-17624. HBASE-17624 made it so one thread only has access
to the rsgroup administrator. In tail of HBASE-17624 [~toffer] describes
scenario under which we may end up in a deadlock (distributed). Let me repeat
[~toffer] comment...
{code}
Both read/write access can't be single threaded. Consider the situation:
1. move_rsgroup_servers is called
2. while #1 is happening rsgroup region is in transition (rpc thread in #1
holds monitor lock)
3. while #2 is happening meta is in transition.
Balancer tries to figure out plan for meta region tries to get monitor lock but
can't. rpc thread task won't release monitor lock since rsgroup region never
gets assigned. rsgroup region never gets assigned because it can't update meta
with new state.
There's a good chance this can be reproduce just by moving both rsgroup and
meta region onto the same RS and call move_rsgoup_servers on the same RS.
A bunch different actors will query from group affiliation so we can't have
writes block reads.
....
In the code prior to this patch the getter methods that retrieve group
information (getRSGroup, ofTable, OfServer, etc) don't require the monitor lock
so the deadlock cycle is broken.
....
The methods that does mutations and updates to zk and hbase:rsgroup are
synchronized appropriately. Point me to where the incoherence is?
{code}
This issue is about testing/fixing/restoring rsgroup access. Will be back.
was:Follow-on from HBASE-17624. HBASE-17624 made it so one thread access to
the rsgroup administrator. In tail of HBASE-17624 [~toffer] describes scenario
under which we may end up in a deadlock (distributed). This issue is to
address this problem.
> HBASE-17624 rsgroup synchronizations will (distributed) deadlock
> ----------------------------------------------------------------
>
> Key: HBASE-17653
> URL: https://issues.apache.org/jira/browse/HBASE-17653
> Project: HBase
> Issue Type: Bug
> Components: rsgroup
> Reporter: stack
> Assignee: stack
>
> Follow-on from HBASE-17624. HBASE-17624 made it so one thread only has access
> to the rsgroup administrator. In tail of HBASE-17624 [~toffer] describes
> scenario under which we may end up in a deadlock (distributed). Let me
> repeat [~toffer] comment...
> {code}
> Both read/write access can't be single threaded. Consider the situation:
> 1. move_rsgroup_servers is called
> 2. while #1 is happening rsgroup region is in transition (rpc thread in #1
> holds monitor lock)
> 3. while #2 is happening meta is in transition.
> Balancer tries to figure out plan for meta region tries to get monitor lock
> but can't. rpc thread task won't release monitor lock since rsgroup region
> never gets assigned. rsgroup region never gets assigned because it can't
> update meta with new state.
> There's a good chance this can be reproduce just by moving both rsgroup and
> meta region onto the same RS and call move_rsgoup_servers on the same RS.
> A bunch different actors will query from group affiliation so we can't have
> writes block reads.
> ....
> In the code prior to this patch the getter methods that retrieve group
> information (getRSGroup, ofTable, OfServer, etc) don't require the monitor
> lock so the deadlock cycle is broken.
> ....
> The methods that does mutations and updates to zk and hbase:rsgroup are
> synchronized appropriately. Point me to where the incoherence is?
> {code}
> This issue is about testing/fixing/restoring rsgroup access. Will be back.
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